Analog broadcasting will finish in 2011 in Japan. Further, analog broadcasting will finish in other developed countries, and is being switched to digital broadcasting. Therefore, a replacement demand for a TV will increase in developed countries until around 2011.
It is, however, predicted that the replacement demand for a TV decreases in developed countries after 2012. Meanwhile, a demand for a TV has been expected to still rise in developing countries in Asia and in South America since 2012 because such developing countries keep a high economic growth rate. It is therefore considered that a TV market centers on the developing countries after 2012.
In the developing countries, however, broadcasting environment is poor. Therefore, in analog broadcasting, an electric field is weak, and video signals become noisy. Further, even in digital broadcasting, video signals become noisy because, frequently, a recorded analog video is converted into a digital video and rebroadcasted. On this account, a noise reducing technique is essential for TVs required in the developing countries.
An example of the noise reducing technique is a low-pass filter. The low-pass filter, however, has a problem of blurring a video while reducing noise.
In order to solve the problem, there has been proposed using an adaptive low-pass filter employing a median filter. FIGS. 18 through 20 each are an explanatory view of an adaptive low-pass filter described in Patent Literature 1.
According to a technique disclosed in Patent Literature 1, a value E1, from a delay circuit 12, of a target pixel to be processed is compared with an output E2 from a three-tap median filter 13 (see FIG. 19), as illustrated in FIG. 18. In a case where the value E1 of the target pixel is larger than the output E2 from the three-tap median filter 13, a noise quantity E3 to be supplied from a noise level detecting circuit 14 is subtracted from the value E1 of the target pixel. In a case where the value E1 of the target pixel is smaller than the output E2 from the three-tap median filter 13, the noise quantity E3 is added to the value E1 of the target pixel. In a case where the value E1 of the target pixel equals to the output E2 from the three-tap median filter 13, the value E1 of the target pixel is outputted as it is.
The noise quantity E3 is detected, by use of the noise level detecting circuit 14, from noise components of a line part having no image signal during a vertical blanking period.
Consequently, a video in which a peak of noise is reduced (see (b) of FIG. 20) is obtained from a video having the noise (see (a) of FIG. 20).